The invention relates to a process for making organic aldehyde compounds from an unsaturated compounds by hydroformylation and in the presence of a catalyst system comprising a Group VIII metal and a bidentate phosphorus ligand having two trivalent phosphorus atoms bound to salicylanilide groups.
Ligands that have trivalent phosphorus atoms are characterized in that each trivalent phosphorus atom is bonded with three organic groups. Phosphorus amide compounds are characterized in that the phosphorus atom is linked to the organic group with at least one Pxe2x80x94N bond and one or two P-0 bonds (also known respectively as phosphorodiamidites and phosphoramidites). Bidentate phosphorus ligands are furthermore characterized in that two phosphorus atoms are present in the molecule and that one organic bridging group (Q) links both phosphorus atoms. The other organic groups bonded to a single phosphorus atom are often called termini groups (R). 
Numerous patents (U.S. Pat. No. 4,769,498, etc.) and other literature describe olefin hydroformylation processes in which an active homogeneous hydroformylation catalyst system is formed by combining rhodium with an organic bidentate phosphite ligand containing two phosphorus atoms linked with an organic dihydroxyl bridging group. The termini groups in these phosphite ligands are most commonly substituted phenol or organic dihydroxyl groups similar to the bridging groups. 
Fewer examples of organic bidentate phosphoramidite ligands have been discovered for olefin hydroformylation with rhodium (WO 9616923, U.S. Pat. No. 5,710,344, etc.). Phosphoramidite ligand examples includes those drawn below. 
However, no prior art has been found that describes an homogeneous rhodium catalyst system for olefin hydroformylation using an organic bidentate phosphite or phosphoramidite ligand comprised of two phosphorus atoms linked by an organic dihydroxyl bridging group with salicylanilide termini groups. Salicylanilides are resonance hybrids of the following two structures. 
Disclosed herein is a hydroformylation process for preparing an organic aldehyde compound from an unsaturated organic compound, said method comprising: contacting an unsaturated organic compound with carbon monoxide, hydrogen gas, and a catalyst system, said catalyst system comprising a Group VIII metal, and at least one or a combination of at least two bidentate organic ligands having two trivalent phosphorus atoms, said ligand selected from the group consisting of structure I, II, III, IV, V, and VI: 
where X1-X4 are C1-C6 alkyl, alkoxy, aryloxy, NR6R7, Cl, F, or CF3; R1 is independently selected from the group consisting of substituted aryl, phenyl, or fused aromatic ring systems; R2 and R3 are independently selected from the group consisting of hydrogen, alkyl, aryl, triarylsilyl, trialkylsilyl, carboalkoxy, carboaryloxy, aryloxy, alkoxy, alkylcarbonyl, arylcarbonyl, or nitrile; R4 and R5 are independently selected from the group consisting of hydrogen, alkyl, alkoxy; R6 and R7 are independently chosen from alkyl and aryl.
Also disclosed are the novel bidentate ligand compositions having two trivalent phosphorus atoms represented by Structures I through VI above.
The present invention provides a hydroformylation process for preparing organic aldehydes using high performing catalyst systems (i.e., selectivity and/or activity) and novel bidentate ligands. A hydroformylation process is used to make the aldehyde from an ethylenically unsaturated compound in the presence of catalyst system that comprises a Group VIII metal or a compound comprising a Group VIII metal, a bidentate ligand having two trivalent phosphorous atoms. When the process according the present invention is used, high selectivities to aldehydes are achieved, combined with a relatively high catalyst activity.
The advantages of this process are even more pronounced when starting from internally unsaturated organic compounds. In comparison to terminal olefins, preparing aldehydes starting from internally unsaturated compounds using previously known hydroformylation processes generally results in lower selectivity to the aldehydes, more hydrogenation of the olefinic double bond and/or lower catalytic activity. An additional advantage of the process according to this invention is that the linearity [linear aldehydes/(linear+branched aldehydes)] is higher.
This object of the present invention is achieved by using at least one ligand of the following formula in a Group VIII metal-catalyzed hydroformylation process: 
where X1-X4 are C1-C6 alkyl, alkoxy, aryloxy, NR6R7, Cl, F, or CF3;
R1 is selected from the group consisting of substituted aryl, phenyl, or fused aromatic ring systems;
R2 and R3 each are independently selected from the group consisting of hydrogen, alkyl, aryl, triarylsilyl, trialkylsilyl, carboalkoxy, carboaryloxy, aryloxy, alkoxy, alkylcarbonyl, arylcarbonyl, or nitrile;
R4 and R5 are independently chosen from the group of hydrogen, alkyl, alkoxy;
R6 and R7 are independently chosen from alkyl and aryl.
Examples of the ligands of the present invention are: 
Salicylanilides may be prepared by the amidation of phenyl salicylates with anilines or by treating salicyl chlorides (often prepared in situ with SOCl2, PCl3, or POCl3 with anilines). Both chemistries can be extended to 1-hydroxy-2-naphthoic or 2-hydroxy-3-naphthoic acid derivatives to prepare the naphthyl analogs.
Salicylanilides can react with phosphorus trichloride (PCl3) to yield compounds where the salicylanilide acts as a dianionic chelate to the phosphorus atom. Two possible product structures (A and B) are shown below that differ in the salicylanilide atoms linked to phosphorus (linkage isomers). For the examples provided below, a single 31P NMR peak in the region of 140 ppm was observed. 
We have found that in the presence of a base, like triethylamine, the product A, B, or a combination of A and B, reacts with organic bridging groups (unsubstituted or substituted 2,2xe2x80x2-biphenol or 1,1xe2x80x2-bi-2-naphthols) to form a single or mixture of ligands that may be used in the process of the present invention. Dependent upon the bridging and salicylanilide groups, the 140 ppm 31P NMR peak for A or B is converted to a single or multiple peaks in the 109-121 ppm region. For the ligand product mixtures, the NMR analysis distinguishes phosphorus atoms in different chemical environments.
The catalyst system of the present invention can be prepared by combining a suitable Group VIII metal or a Group VIII metal compound with a phosphorus-containing ligand, optionally in a suitable solvent, in accordance with methods known for forming complexes.
Examples of suitable Group VIII metals are ruthenium, rhodium, and iridium. Examples of suitable Group VIII metal compounds are, for example, Ru3(CO)12, Ru(NO3)3, RuCl3(Ph3P)3, Ru(acac)3, Ir4(CO)12, IrSO4, RhCl3, Rh(NO3)3, Rh(OAC)3, Rh2O3, Rh(acac)(CO)2, [Rh(OAc)(COD)]2, Rh4(CO)12, Rh6(CO)16, RhH(CO)(Ph3P)3, [Rh(OAc)(CO)2]2, and [RhCl(COD)]2 (wherein xe2x80x9cacacxe2x80x9d is an acetylacetonate group; xe2x80x9cAcxe2x80x9d is an acetyl group; xe2x80x9cCODxe2x80x9d is 1,5-cyclo-octadiene; and xe2x80x9cPhxe2x80x9d is a phenyl group). However, it should be noted that the Group VIII metal compounds are not necessarily limited to the above listed compounds. The source for the Group VIII metal is preferably rhodium. The source for suitable Group VIII metal compounds include, but are not limited to, hydrides, halides, organic acid salts, acetylacetonates, inorganic acid salts, oxides, carbonyl compounds and amine compounds of Group VIII metals.
The unsaturated organic compound that is used in the present invention must have at least one xe2x80x9cCxe2x95x90Cxe2x80x9d bond in the molecule, and preferably, 2 to 20 carbon atoms. Suitable ethylenically unsaturated organic compounds for use in the present invention include, but are not limited to, linear terminal olefinic hydrocarbons. Some examples of these are ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and 1-dodecene; branched terminal olefinic hydrocarbons, for example isobutene and 2-methyl-1-butene; linear internal olefinic hydrocarbons, for example cis- and trans-2-butene, cis- and trans-2-hexene, cis- and trans-3-hexene, cis- and trans-2-octene and cis- and trans-3-octene; branched internal olefinic hydrocarbons, for example 2,3-dimethyl-2-butene, 2-methyl-2-butene and 2-methyl-2-pentene; terminal olefinic hydrocarbon-internal olefinic hydrocarbon mixtures, for example octenes prepared by dimerization of butenes, olefin oligomer isomer mixture of from dimer to tetramer of lower olefins including propylene, n-butene, isobutene or the like; and cycloaliphatic olefinic hydrocarbons for example cyclopentene, cyclohexene, 1-methylcyclohexene, cyclooctene and limonene. Butadiene, methallyl acetate, 3-pentenoic acid, and unsaturated organic compounds having 6 to 20 carbon atoms, such as alkyl 3-pentenoates, are also useful in the present invention.
Suitable olefinic compounds include those substituted with an unsaturated hydrocarbon group including compounds containing an aromatic substituent such as styrene, xcex1-methylstyrene and allylbenzene; and diene compounds such as butadiene, 1,5-hexadiene, 1,7-octadiene and norbornadiene. It has been found that with the process according to this invention it is possible to prepare 3-pentenal from butadiene in high yield.
The unsaturated organic compound can be substituted with one or more functional groups containing a heteroatom, such as oxygen, sulfur, nitrogen or phosphorus. These heteroatom substituted unsaturated organic compounds include, but are not limited to, vinyl methyl ether, methyl oleate, oleyl alcohol, allyl alcohol, methallyl alcohol, methallyl acetate, methyl 2-pentenoate, methyl 3-pentenoate, methyl 4-pentenoate, 3-pentenoic acid, 4-pentenoic acid, 1,7-octadiene, 7-octen-1-al, acrylonitrile, acrylic acid esters, methylacrylate, methacrylic acid esters, and methylmethacrylate.
A special class of internally unsaturated organic compounds is 3-pentenoic acid and C1-C6 alkyl 3-pentenoate ester compounds. Terminal aldehyde compounds prepared by the disclosed process starting from these compounds can be used advantageously in the preparation of xcex3-caprolactam or adipic acid, which are precursors for respectively Nylon-6 and Nylon-6,6. Examples of C1-C6 alkyl 3-pentenoates are methyl-, ethyl-, propyl-, isopropyl-, tert-butyl-, pentyl and cyclohexyl 3-pentenoate. Methyl and ethyl 3-pentenoate esters are preferred because they are more readily available.
The 3-pentenoic acid and C1-C6 alkyl 3-pentenoate ester compounds may be present in mixtures containing, respectively, 2- and 4-pentenoic acid; and C1-C6 alkyl 2- and 4-pentenoate ester compounds. Since these compounds react in a similar fashion as the 3-isomer to the desired terminal aldehyde, a mixture of isomers can be directly used in the process according to the invention.
The hydroformylation process is carried out under conditions that will be dependent on the particular starting unsaturated organic compound. The temperature for the reaction can be from about room temperature to about 200xc2x0 C., preferably from about 50xc2x0 C. to about 150xc2x0 C. The pressure may vary from normal pressure to 20 MPa, preferably from 0.15 to 10 Mpa, and more preferably from 0.2 to 5 MPa. The pressure is, as a rule, equal to the combined hydrogen and carbon monoxide partial pressure. Extra inert gases may, however, be present. The molar ratio of hydrogen:carbon monoxide is generally between 10:1 and 1:10, and preferably between 6:1 and 1:2.
In general, the concentration of Group VIII metal or Group VIII metal compound in the reaction medium is between 10 and 10,000 ppm, and more preferably between 100-1000 ppm, calculated as free metal.
The molar ratio of multidentate phosphorus ligand to Group VIII metal or Group VIII metal compound is from about 0.5 to 100, and preferably from 1 to 10 (mol ligand/mol metal).
The solvent may be a mixture of reactants from the hydroformylation itself, such as the starting unsaturated compound, the aldehyde product and/or by-products. Optionally, a solvent that is not a mixture of the reactants may be used. Solvents that are suitable for use in the present invention include saturated hydrocarbons (for example kerosene, mineral oil, or cyclohexane), ethers (for example diphenyl ether or tetrahydrofuran), ketones (for example acetone, cyclohexanone), nitrites (for example acetonitrile, adiponitrile or benzonitrile), aromatics (for example toluene, benzene or xylene), esters (for example methyl valerate, caprolactone), Texanol(copyright) (available from Union Carbide), or dimethylformamide.